add method as_iterator to abstract ListResource
add tests for calling Call.as_iterator()
add variable chunk size to avoid extra looping
Inspect as_iterator in ListResource; override as_iterator in class Media and some tests for as_iterator
ListResource while True instead chunks_amount and Tests test_as_iterator_query_params for all classes
some pep fixes and fix unnecessary request data in tests
Merge pull request #6 from bandwidthcom/as_iterator_1.0.4

add method as_iterator to abstract ListResource